The invention relates to a storage assembly for storing coolant medium circulating in a cooling circuit of a cooling system, which storage assembly is in particular suitable for use in a cooling system designed for an operation with a two-phase coolant medium for cooling food on board an aircraft.
Cooling systems suitable for an operation with a two-phase coolant medium are known from DE 10 2006 005 035 B2 and DE 10 2009 011 797 A1 and are used, for example, for cooling food that is stored on board a passenger aircraft and that is to be distributed to the passengers. The food that is to be given to the passengers is typically kept in mobile transport containers. The transport containers are filled outside the aircraft, pre-cooled and, after being loaded into the aircraft, placed in corresponding storage positions in the aircraft passenger cabin, for example in the galleys. In order to ensure that the food remains fresh until it is distributed to the passengers, cooling stations are provided in the region of the transport container storage positions, which cooling stations are supplied with cooling energy from a central cold-producing device and deliver that cooling energy to the transport containers with the food stored therein.
The advantages of a cooling system with a central cold-producing device over cold-producing units provided separately at the individual transport container storage positions are that it has a smaller installation space and a lower weight, and in addition it requires a lower outlay in terms of assembly and maintenance. In addition, the use of a cooling system that has a central cold-producing device arranged outside the passenger cabin makes it possible to avoid machine noises which are produced by cold-producing units positioned in the region of the transport container storage positions and which can be heard in the aircraft passenger cabin and may accordingly be perceived as disturbing.
In the cooling systems known from DE 10 2006 005 035 B3 and DE 10 2009 011 797 A1, the phase changes of the coolant medium flowing through the cooling circuit of the cooling systems that take place during operation of the system allow the latent heat consumption that occurs thereby to be used for cooling purposes. The mass flow of coolant medium required to provide a desired cooling efficiency is therefore significantly lower than, for example, in a liquid cooling system in which a single-phase liquid coolant medium is used. Consequently, the cooling systems described in DE 10 2006 005 035 B3 and DE 10 2009 011 797 A1 can have smaller pipe cross-sections than a liquid cooling system of comparable cooling efficiency. Furthermore, the reduction in the mass flow of coolant medium allows the conveying power required to convey the coolant medium through the cooling circuit of the cooling system to be reduced. This results in increased efficiency of the system, because less energy is required to operate a corresponding conveying device, such as, for example, a pump, and, moreover, less additional heat generated by the conveying device during operation of the conveying device has to be dissipated from the cooling system.
In the cooling systems known from the prior art, the two-phase coolant medium is conventionally stored intermediately in the form of a boiling liquid in storage containers which are integrated into the cooling circuits of the cooling systems. In order to avoid increased wear of a conveying device, for example in the form of a pump, for conveying coolant medium from a storage container, the conveying of steam through the conveying device and the formation of steam bubbles (cavitation) in the conveying device must be prevented as far as possible.
To that end, corresponding subcooling of the coolant medium stored intermediately in the storage containers is necessary. That is generally brought about by a pressure increase, which is generally achieved by arranging a suction nozzle of the conveying device in a defined position beneath a sump of the storage container, from which the coolant medium stored intermediately in the storage container is discharged from the storage container. In other words, the conveying device is so positioned relative to the storage container that a minimum positive suction head, which is defined by the height of a column of liquid above a leading edge of a moving blade of the conveying device, is maintained for the conveying device. The force of gravity of the column of liquid causes a defined pressure build-up in the coolant medium fed into the conveying device and thus effects subcooling of the coolant medium, that is to say prevents condensation of the coolant medium.
When installing a cooling system in an aircraft, however, the problem frequently occurs that it is difficult to accommodate the system components in the only very limited installation space or even, as described above, to position them relative to one another so that, for example, by using the force of gravity of a column of liquid above a leading edge of a moving blade of a conveying device, a pressure increase in the coolant medium fed to the conveying device can be achieved, thus preventing condensation of the coolant medium by the pressure reduction caused by the conveying device.
DE 10 2011 014 954, which is not prior-published, therefore proposes equipping a storage assembly which is suitable for use in a cooling system designed for an operation with a two-phase coolant medium for storing coolant medium circulating in a cooling circuit of the cooling system with a liquefier which is configured to condense coolant medium which is to be received in a receiving area of the storage container before it is fed into the receiving area of the storage container. The storage assembly further comprises a heat exchanger which is arranged in the receiving area of the storage container and which ensures that coolant medium discharged from the receiving area of the storage container is always subcooled sufficiently. As a result, it is ensured that the coolant medium is always fed in the liquid state to a conveying device for discharging coolant medium from the receiving area of the storage container.